Presses

ABSTRACT

A C-FRAME PRESS IN WHICH GAPING OF THE GAP DUE TO THE PRESSING FORCE IS MINIMISED BY PROVIDING A TIE-BAR ACROSS THE GAP ASSOCIATED WITH TENSIONING MEANS WHICH APPLY TO THE TIE-BAR A TENSION SUBSEQUENTLY PROPORTIONAL TO THE PRESSING FORCE. D R A W I N G

' I- H. v. NORTON ETAL 3,561,252

PRESSES 2 Sheets-Sheet l Filed Feb .1969

United States Patent Oihce US. Cl. 72455 9 Claims ABSTRACT OF THEDISCLOSURE A C-frame press in which gaping of the gap due to thepressing force is minimised by providing a tie-bar across the gapassociated with tensioning means which apply to the tie-bar a tensionsubstantially proportional to the pressing force.

This invention relates to presses of what may be termed the open-frameor C-frame type. The invention will be described for convenience inrelation to upright presses in which a forwardly projecting lowerportion of the frame supports a fixed press tool, while an overhangingupper portion of the frame carries a vertically movable press toolactuated by a crank mechanism or a hydraulic ram. It is to beunderstood, however, that the invention is applicable to presses of theC-frame type generally, irrespective of whether the motion of themovable press tool is vertical, horizontal or inclined.

In a press of the C-frame type the reaction to the pressing forceapplies a bending moment to the frame which tends to cause the gap ofthe C to widen or gape. This may produce misalignment of the press toolsor other disadvantages.

Also, when the pressing force is released the elasticity of the framecauses the gap to narrow again but the inertia of the frame causes thegap to narrow too much so that a reversed bending moment is applied. Theelasticity of the frame then widens the gap again, and so on, the framevibrating at its natural resonant frequency until the energy stored inthe frame by the initial bending has been dissipated. This vibration notonly wastes energy but also causes noise, wear and inaccuracy.

According to the present invention, a press of the C- frame type isprovided with at least one tie-rod across the gap of the frame andtensioning means adapted to apply to the tie-rod a tensile forcesubstantially proportional to the pressing force.

Thus gaping of the frame is wholly or substantially eliminated and theabove-mentioned disadvantageous effects of misalignment and vibrationare minimised.

In one form of the invention one end of the tie-rod is attached directlyto the frame above or below the gap and the other end of the tie-rod isattached to the frame below or above the gap indirectly through thetensioning means. In the case of a hydraulic press the tensioning meansmay be connected to a high pressure part of the hydraulic system of thepress. Thus, as the pressure in the hydraulic system rises, the pressurein the hydraulic tensioning means rises also and applies an increasingtension to the tie-rod. In the case of a mechanical crank press thehydraulic tensioning means could be actuated by means of a source ofhydraulic pressure such as a high pressure pump which supplies fluid tothe tensioning means at a pressure determined by load-sensing meansassociated with the crank mechanism.

If the tie-rod were omitted, the pressing force would cause the frame togape by elastically bending the frame Patented Feb. 9, 1971 about animaginary centre somewhere to the rear of the gap, the position of thiscentre depending upon the geometry of the frame. Preferably, in the caseof a hydraulic press, the ratio between the effective pressurised areaof the hydraulic tensioning means and the effective area of thehydraulic ram is substantially equal to the inverse ratio between therespective distances of their axes of operation from the said centre. Inthis way the bending moment produced on the frame by the hydraulicpressing force is substantially counterbalanced by the bending momentproduced in the opposite direction by the hydraulically tensionedtie-rod.

In one form of the invention, the tensioning means comprises an annularhydraulic piston and cylinder arrangement, one end portion of thetie-rod passing through this annular arrangement and the annular pistonbearing against a collar or shoulder at this end of the tie-rod. Theother end of the tie-rod may be attached to the frame directly in aquickly detachable manner. This permits 20 the latter end of the tie-rodto be quickly detached and the tie-rod moved out of the way bywithdrawing the tie-rod through the tensioning means, to facilitateaccess to the gap of the press, for example, when setting up the presstools.

Alternatively, one end of the tie-rod may be directly attached to theframe in a quickly detachable manner and the tensioning means may bepivotally attached to the frame to enable the tie-rod to be swung clearof the gap, when not under tension, without removing it from the 30tensioning means.

In another form of the invention the tensioning means act upon the rearend of a lever the front end of which is pivoted to the front portion ofthe frame below or above the gap, one end of the tie-rod being connectedto 35 an intermediate point of the lever and its other end beingconnected to the frame above or below the gap. This arrangement enablesa smaller tensioning means to be used, advantage being taken of theleverage to increase the tensioning force. It also has the advantagethat the 4.0 end of the tie-rod connected to the lever is disposedfurther to the rear than would otherwise be possible, to afford accessto the gap without having to remove or displace the tie bar.

In the case of a hydraulic press, a pressure line may connect the highpressure side of the ram with the hydraulic tensioning means so that theforce applied to the tie-rod by the tensioning means is directlyproportional to the pressing force.

The invention may be performed in various ways and some specificembodiments will now be described by way of example wth reference to theaccompanying diagrammatic drawings, in which:

FIG. 1 is a side view of a C-frame press of the hydraulic ram type,shown partly in section;

FIG. 2 is a fragmentary section showing one arrangement for theconnection of the tie-rod to the tensioning means and to the frame;

FIG. 3 is a fragmentary cross-section taken on the line III-1II in FIG.2;

FIG. 4 is a diagrammatic view of an arrangement having a pivotedtensioning means;

FIG. 5 shows another embodiment, employing a lever;

FIG. 6 is a side view of a further embodiment in which the pressoperates by a crank mechanism; and

FIG. 7 is a view similar to FIG. 3, showing another form of attachmentof the tie-rod to the frame.

Referring to FIG. 1, there is shown a C-frame press 10 of the hydraulicram type. The frame 11 of the press is generally in the form of a letterC, having a gap 12 in which the pressing operation takes place. Thelower portion 13 of the frame below the gap carries a fixed press tool14 on which is placed a workpiece 15 to be subjected to the pressingoperation. The upper portion 16 of the frame above the gap accommodatesthe hydraulic ram mechanism. This comprises a cylinder 17 in which canslide a piston 18 connected to a piston rod 19 which passes out throughthe lower end of the cylinder 17 through a seal 20. At the lower end ofthe piston rod 19 is fitted a movable press tool 21. The piston 18,piston rod 19 and movable press tool 21 are forced downwards to performthe pressing operation by means of high pressure hydraulic fiuidadmitted through a line 23 to the cylinder 17 below the piston 18. Thehydraulic system for raising and lowering the piston is conventional andis not further illustrated or described.

If the press as so far described were operated to perform a pressingoperation, the reaction to the downward force exerted on the press tool.21 by means of the hydraulic ram parts 17, 18 and 19 would produce abending moment on the frame 11 about an imaginary centre 24 somewhere tothe rear of the gap 12, tending to enlarge the gap. This would have twoadverse effects. In the first place the bending of the frame could causesome misalignment of the working parts with consequent wear, and of thepress tools with consequent inaccuracy. Secondly, the elasticity of theframe would tend to cause it to virbrate at its natural resonantfrequency, as already described.

The additional parts provided in accordance with the invention and nowto be described minimise these adverse effects.

Secured to the front of the lower portion 13 of the frame is a bracket25. Pivotally attached to the bracket 25 by means of a pin 26 is atie-rod 27 which extends across the gap 12. The upper end of the tie-rod27 is connected to the upper portion 16 of the frame through tensioningmeans 28. The tensioning means illustrated in FIG. 1 comprises ahydraulic cylinder 29 containing a piston 30 fixed to the upper end ofthe tie-rod 27. The tie-rod 27 passes through the lower end wall of thecylinder 29 and is sealed by means of a seal 31. A conduit 32 connectsthe cylinder space below the piston 30 of the tensioning means to thecylinder space above the piston 18 of the hydraulic ram. Thus, when thehydraulic ram is on its working stroke and the space above the piston 18is under pressure, this pressure is transmitted through the conduit 32to the under-side of the piston 30 so that the tie-rod 27 is placedunder tension, this tension opposing the hydraulic ram force which wouldotherwise tend to widen the gap 12 as already described.

The axis 33 of the hydraulic ram and the axis 34 of the tie-rod arerespectively at distances A and B from the parallel axis 35 through thecentre of bending 24. The leverage by which the tension in the tie-rod27 opposes the leverage of the hydraulic ram tending to produce thebending is in the ratio B/A. By making the areas of the pistons 30 and18 in the inverse ratio A/B, the bending effect produced by thehydraulic ram is substantially neutralized by the tension in thetie-rod. Thus, bending of the frame does not occur and the adverseeffects which would otherwise arise are minimised.

As the tie-rod 27 is in front of the gap 12 its presence may reduceaccessability to the workpiece and press tools. To facilitate access tothe gap, the tie-rod may be made removable as shown in FIGS. 2 and 3.For this purpose the tensioning means is in the form of an annularcylinder 41, the cylinder containing an annular piston 42. The upper endof the tie-rod 37 passes through the hollow interior space 43 of thecylinder 41 and is provided at its :upper end with a collar or shoulder44. The piston 42 bears against the underside of the collar or shoulder42, being provided for this purpose with a tubular extension or sleeve45. The cylinder space below the piston 42 is connected to the conduit32.

At the lower end of the tie-rod 37 there is an annular groove 46 whichfits into a slot 47 in a bracket 48. The width of the slot 47 isnarrower than the diameter of the tie-rid 37, so that the tie-rod isrestrained against vertical movement relative to the bracket 48. When itis desired to remove the tie-rod, while it is not under tension, it isswung forward slightly until the annular groove 46 is clear of the slot47 in the bracket. The clearance in the interior space 43 of thetensioning means is suflicient to permit this. The tie-rod can then bewithdrawn upwardly through the interior space 43. After the press toolshave been set up, the tie-rod is replaced by reversing the procedure.

A modified form of attachment for the lower end of the tie-rod is shownin FIG. 7. Instead of being provided with an annular groove 46 as shownin FIGS. 2 and 3, the lower end of the tie-rod 54 has a pair of lugs 49which ordinarily lie beneath side portions 50 of the bracket 51. When itis desired to remove the tie-rod 54, while not under tension, it isrotated through 90 so that one of the lugs is in register with a gap 52in the bracket behind the tie-rod while the other lug is in registerwith a gap 53 in front of the tie-rod. The tie-rod 54 can then beremoved by raising it through the hollow interior space 43 of thetensioning means. Since the tie-rod does not have to be tilted, theclearance in the space 43 can be very small. If it is desired to removethe tie-rod 54 completely, the lugs 49 can be detachable, but generallysufficient accessability is obtained merely by raising the tie-rod.

Another arrangement for affording accessibility is shown in FIG. 4. Thisdoes not necessitate removing or raising the tie-rod. The lower end ofthe tie-rod 57 is attached to the lower portion of the frame in areadily detachable manner, such as already described with reference toFIGS. 2 and 3. In this case the tensioning means 28 is as shown in FIG.1, but is attached to the upper portion of the frame by a pivot 55 sothat when the lower end of the tierod 57 has been released thetensioning means and the tierod can be tilted sideways as shown indotted lines in FIG.

4. The fluid conduit is a length of flexible piping 56 connected to somepoint in the high pressure part of the hydrauli ram system.

Another way of facilitating access to the gap 12 and to the partstherein is shown in FIG. 5. In this case the tensioning means 60 issecured to the rear of the frame 10, the cylinder space above the piston61 of the tensioning means being connected to a high pressure part ofthe hydraulic ram system by a line 62. A piston rod 63 attached to thepiston 61 of the tensioning means is connected to a pivot 64 at the rearend of a lever 65 the front end of which is pivoted at 66 to the side ofthe lower portion 13 of the frame. The arrangement is such that when thehydraulic ram is performing its working stroke under pressure, thetensioning means is tending to force the lever downwards about the pivot66. Pivoted at 67 to the side of the upper portion 16 of the frame is aninclined tie-rod 68. The lower end of this tie-rod is pivoted at 69 toan intermediate point of the lever 65. Thus, the downward force on thelever imparted by the tensioning means 60 applies a tensile force to thetie-rod 68. The dimensions of the various parts described are such thatthe force tending to narrow the gap 12, applied by the upward reactionat the front end 66 of the lever 65 and the downward force applied atthe pivot 67 by the tension of the tie-rod 68, substantiallycounterbalances the hydraulic ram force tending to widen the gap, sothere is virtually no tendency for the frame to bend about the point 24.

FIG. 6 shows the application of the invention to a press 70 of themechanical crank type. In this case the movements of the press tool 21are provided by means of a rotary crank 71 the crank pin 72 of which isconnected to the upper end of a connecting rod 73. The movable presstool 21 is mounted on the lower end of a slide member 74 whichreciprocates in guides 75. The upper end of the slide member isconnected to the lower end 76 of the connecting rod 73 through aload-sensing device 77. This device consists of a cylinder 78 connectedto the lower end 76 of the connecting rod and containing a piston 79connected to the upper end of the slide member 74. The cylinder spaceabove the piston 79 contains hydraulic fluid which is put under pressureon the working stroke of the press.

Mounted on the lower portion 13 at the front of the press is a bracket25 to which is connected a tie-rod 27 as shown in FIG. 1. Similarly, onthe front of the upper portion 16 of the press there is providedtensioning means 28 as shown in FIG. 1. A flexible pipe 82 connects theupper cylinder space of the load-sensing device 77 to the lower cylinderspace of the tensioning means 28. The pipe 82 thus transmits to thetensioning means a hydraulic pressure equal to that in the load-sensingdevice and therefore proportional to the pressing force. The dimensionsare so selected that the tension in the tie-rod 27 substantiallycounterbalances the reaction of the mechanical pressing force.

Various modifications can be made to the constructions described. Forexample, the arrangement shown in FIG. 6 can utilise an electricalload-sensing device such as a strain gauge, connected through suitableelectronic circuitry to any appropriate form of tensioning means, e.g.it could influence a pressure control valve of a hydraulic tensioningsystem. The tensioning means could be other than hydraulic, e.g.mechanical or pneumatic. There could be two or more tie bars and two ormore tensioning means.

What we claim as our invention and desire to secure by Letters Patentis:

1. A press comprising a C-frame having a rear portion, a front upperportion and a front lower portion spaced by a gap from said front upperportion, means in one of said front portions to apply a pressing forceto a workpiece inserted in said gap, at least one tie-rod extendingacross said gap, tensioning means, and an operative connection betweensaid tensioning means and said tie-rod to apply to said tie-rod atensile force substantially proportional to said pressing force.

2. A press according to claim 1 including first attachment meansattaching one end of said tie-rod directly to one of said front portionsof said frame, second attachment means attaching the other end of saidtie-rod to said tensioning means, and means attaching said tensioningmeans to the other of said front portions of said frame.

3. A press according to claim 1 including a lever having a front pivot,a rear pivot and an intermediate pivot, means connecting said tensioningmeans to said rear pivot, said front pivot being connected to one ofsaid front portions of said frame, said intermediate pivot beingconnected to one end of said tie-rod, and the other end of said tierodbeing connected to said other front portion of said frame.

4. A press according to claim 2 in which said tie-rod has a shoulder atone end, said tensioning means comprises an annular piston and anannular hydraulic cylinder. said end of said tie-rod passing throughsaid annular piston and cylinder with said annular piston bearingagainst said shoulder, and said first attachment means is quicklydetachable.

5. A press according to claim 2 in which said first attachment means isquickly detachable and said tensioning means is pivotally attached tosaid frame enabling said tie-rod to be swung clear of said gap.

6. A press according to claim 1 which is a hydraulic ram press and saidtensioning means is hydraulic, and which includes a connectionconnecting said tensioning means to a high pressure part of saidhydraulic ram press.

7. A press according to claim 6 in which the ratio between the eifectivepressurized area of said hydraulic tensioning means and the effectivearea of said hydraulic ram is substantially equal to the ratio betweenthe distances of said hydraulic ram and of said hydraulic tensioningmeans from the centre of bending of said frame due to said pressingforce.

8. A press according to claim 1 which is a mechanical crank press andwhich includes load-sensing means associated with the crank mechanism,control means to influence the tension applied to said tie-rod by saidtensioning means, and means responsive to said load-sensing means toactuate said control means.

9. A press according to claim 8 in which said tensioning means ishydraulic and said load-sensing means influences the hydraulic pressureapplied to said tensioning means.

CHARLES W. LANHAM, Primary Examiner G. P. CROSBY, Assistant Examiner US.Cl. X.R.

